1. Field of the Invention
The present invention relates to a fabrication method of metallic nanowire, and more particularly, to a fabrication method of a metallic nanowire that is capable of growing a large amount of nanowires on a substrate without a lithography process and heterogeneous catalytic metal.
2. Description of the Background Art
The metallic nanowire, usually fabricated by a highly fine etching process, are used as a probe of an atomic force microscope (AFM) or a scanning tunneling microscope (STM), or an electron emission tip of an electron emission display device.
As the semiconductor device is scaled down and integrated at a fast and continual pace compared with the trend in those past years, it is expected that the use of metallic nanowire or nano-rods in the field of nanoelectronics and nanomechanics will continue to increase. Up to now, the minimum size of a metal nanowire implemented in a silicon as a product is about 0.35 xcexcm and it is expected that the size would be reduced to the level of about 0.1 xcexcm. However, with a conventional lithography process, it is difficult to form the metallic nanowire of below 0.1 xcexcm. Therefore, a novel method has been required in forming metallic nanowires on a semiconductor substrate.
Recently, the xe2x80x98bottom-upxe2x80x99 method of fabricating a high integrated semiconductor device with the nano size without being much dependent on the lithography technique have been adopted in a self-assembly growth and the growth of a nano wire or a nano-rod of a first-dimensional quantum wire.
Thus, in fabrication of the semiconductor device, it is expected that the current xe2x80x98top-downxe2x80x99 method will be replaced with a xe2x80x98bottom-upxe2x80x99 method. The former has an advantage that it can accomplish an integrated semiconductor device with an excellent regularity and reproducibility on the basis of the established technique, but it has shortcomings that it is absolutely dependent on the lithography technique development. Conversely, since the latter uses a mechanism that a material itself of a semiconductor device is formed with a nano size in fabrication of the semiconductor device, it does not have a dependence on the lithography technique. But the difficulty in reproducibility and standardization leads to the difficulty in integration of a molecular device of a high yield.
As shown in FIGS. 1 and 2, a bulk material is processed by fine etching, so that the tip of it may get sharper as it goes upward from the wide base. In such a case, since the fabricated tips have different shapes, it is difficult to standardize them.
In addition, it is not easy to uniformly etch and form the tips in a hole with 1 xcexcm size in case of using the tips as a field emission source of the field emission display device or an amplifier.
Therefore, an object of the present invention is to provide a fabrication method of metallic nanowires that is capable of growing a large amount of metallic nanowires on a substrate by in-situ process without both a lithography process and heterogeneous catalytic metal.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a fabrication method of metallic nanowires including the steps of: forming a layer of autocatalytic metal with a thickness of 30 nm-1000 nm on the surface of a substrate; and forming nanowires on the front surface of the layer of autocatalytic (or self-catalytic) metal, wherein the substrate is put into an furnace (or process chamber) and the layer of autocatalytic metal is grown by autocatalytic reaction for 10xcx9c5000 seconds.
In the fabrication method of metallic nanowires according to the invention, the nanowire growth time is important and the reason is as follows.
In order for the layer of autocatalytic metal to be grown to metallic nanowires by the autocatalytic reaction, a stress more than a specific value by a thermal energy should exist in the layer of autocatalytic metal. In order to make such an effect, the growth time needs to be above 10 sec. However, if the growth time exceeds 5000 sec, the grown nanowires lumps to be transited to a conventional continuous film form.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.